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Persistence of Escherichia coli on injured iceberg lettuce in the field, overhead irrigated with contaminated water
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posted on 2009-03-01, 00:00 authored by F Barker-Reid, D Harapas, S Engleitner, S Kreidl, R Holmes, Robert FaggianRobert FaggianFresh produce is increasingly implicated in food-related illnesses. Escherichia coli can survive in soil and water and can be transferred onto plant surfaces through farm management practices such as irrigation. A trial was conducted to evaluate the impact of field conditions on E. coli persistence on iceberg lettuce irrigated with contaminated water, and the impact of plant injury on the persistence of E. coli. Lettuce heads were injured at 14, 7, 3, 2, 1, and 0 days before inoculation, with uninjured heads used as a control. All lettuce heads (including controls) were overhead irrigated with a mixture of nonpathogenic E. coli strains (10^sup 7^ CFU/ml). E. coli counts were measured on the day of inoculation and 5 days after, and E. coli was detected on all lettuce head samples. Injury immediately prior to inoculation and harvest significantly (P = 0.00067) increased persistence of E. coli on lettuce plants. Harsh environmental conditions (warm temperatures, limited rainfall) over 5 days resulted in a 2.2-log reduction in E. coli counts on uninjured lettuce plants, and lettuce plants injured more than 2 days prior to inoculation had similar results. Plants with more recent injuries (up to 2 days prior to inoculation) had significantly (P = 7.6 × 10^sup -6^) greater E. coli persistence. Therefore, growers should postpone contaminated water irrigation of lettuce crops with suspected injuries for a minimum of 2 days, or if unavoidable, use the highest microbiological quality of water available, to minimize food safety risks.
History
Journal
Journal of food protectionVolume
72Issue
3Pagination
458 - 464Publisher
International Association for Food ProtectionLocation
Des Moines, IowaISSN
0362-028XLanguage
engPublication classification
C1.1 Refereed article in a scholarly journalUsage metrics
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